1. Field of the Invention
The present invention relates to a circuit for reference current and voltage generation, and more particularly, to a circuit for reference current and voltage generation used in a hand-held electronic device.
2. Description of the Related Art
Since the application of hand-held electronic devices is more popular now, the requirement of the battery usage time is more demanded. How to reduce the power consumed by the electronic components in the hand-held electronic apparatus when it is in a stand-by or turned-off state had become a major subject of the current technology development. For the analog circuit, the static current consumed in the circuit for reference current and voltage generation is usually a technique bottleneck. Accordingly, it is desired to develop a new circuit for reference current and voltage generation, in which the circuit is easily turned on and off, and only a very small static current is consumed when it is in the turned-off state.
A circuit shown in FIG. 1 had been disclosed in U.S. Pat. No. 5,949,227, in which a startup circuit 101 is configured to turn on the voltage reference circuit 103, and a startup disabling circuit 102 is configured to isolate the startup circuit 101 and the voltage reference circuit 103 when the circuit in FIG. 1 is in the turned-off state. However, the startup disabling circuit 102 proposed in this patent cannot fully turn off the current. In other words, there is still some current consumption when the circuit is in the turned-off state.
A low voltage bandgap reference circuit had been disclosed in the thesis “A CMOS Bandgap Reference Circuit with Sub-1-V Operation” proposed by Hironori Banba and Hitoshi Shiga et al. in Journal of Solid-State Circuit, vol. 34, no. 5, pp. 670-674, May 1999. In the method for turning on the bandgap reference circuit proposed by this thesis, an n-channel metal oxide semiconductor field effect (NMOS) transistor and a power-on reset signal are used to start up the whole circuit when the electric power is just provided to the bandgap reference circuit. Even this thesis had proposed a method to implement the low voltage bandgap reference circuit and a method for turning on the circuit, a method for turning off the circuit was never mentioned.
Another thesis “Curvature-Compensated BiCMOS Bandgap with 1-V Supply Voltage” had proposed by Piero Malcovati and Franco Maloberti et al. in Journal of Solid-State Circuit, vol. 36, no. 7, pp. 1076-1081, July 2001. This thesis mainly proposed a method for designing an operational amplifier (OP AMP) in the bandgap reference circuit under low voltage and a method for turning on the circuit. However, a method for turning off the circuit is absent. In addition, a BiCMOS manufacturing process is required in the method for turning on the circuit mentioned above. In other words, the implementation of such a method requires a composite manufacturing process of bipolar junction (BJT) transistors and complementary MOS transistors (CMOS).
In summary, the current technique fails to fulfill our expectation.